Magnetic-field-induced strain (MFIS) is the longitudinal deformation exhibited by magnetic shape-memory alloys (MSMA). MFIS is carried out by crystallographic twinning and produces an axial actuation stroke of up to the twinning strain (e.g. 6% for 10M Ni—Mn—Ga). MFIS may be harnessed to perform actuation operations. Examples, of actuation applications that are based on MFIS include micropumps as described in U.S. patent application Ser. No. 13/550,386 filed on Jul. 16, 2012 and entitled “Actuation Method and Apparatus, Micropump, and PCR Enhancement Method,” now U.S. Pat. No. 9,091,251 and U.S. patent application Ser. No. 14/493,674 filed on Sep. 23, 2014 and entitled “Electrically Driven Magnetic Shape Memory Apparatus and Method,” the contents of each of which are hereby incorporated by reference in their entirety.
For typical applications relying on MFIS, a stroke associated with the actuation member is relatively small compared to the length of the actuation member (on the order of 6%). What is needed is an actuation device with a long stroke. Further, in these applications, the work output of the actuation member is limited by its magnetocrystalline anisotropy energy. As such, MSMA actuation members that rely purely on longitudinal MFIS for actuation may not be sufficient for some applications.